Monitor Linux VM Disk Space

We have a Linux machine that is currently being used as a mount point for another server. This server does nightly backups of our ERP system, and I was wondering if it was possible to set up a monitor via SNMP to monitor the available free space on the machine and make sure it doesn't get too small. Currently, we're running it Hyper-v on Server 2012 R2. The Linux VM itself is Red Hat 6.6. Whenever I try and add a performance monitor, however, I get the below message.

Please check whether the device is SNMP enabled and check the community strings.

I also do not seem to the option to add a VM performance monitor. However, when I test the get community string with the "Click here to change" passwords option, it successfully verifies connectivity. Am I doing something wrong or is what I'm doing unsupported?